To meet the demand for wireless data traffic having increased since deployment of 4G communication systems, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’.
The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like.
In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
In a multi-cell wireless communication system, Gaussian assumption is applied on an interference signal to perform decoding at a low complexity. In the case of assuming Gaussian characteristic for the interference signal, a Quadrature Amplitude Modulation (QAM) series modulation scheme is used frequently to make the interference signal to the real transmission signal to have the Gaussian characteristic.
In consideration of the channel characteristics, however, it is preferred for the transmitter and receiver to use the non-Gaussian characteristic instead of the Gaussian characteristic to improve the decoding performance as well as throughput.
Recently, many studies are being conducted on the modulation scheme which gives the non-Gaussian characteristic to the interference signal for use in the wireless communication system. Frequency and Quadrature Amplitude Modulation (FQAM) is one of the representative modulation schemes resulted from such studies. The FQAM scheme is a hybrid modulation scheme developed by combining a QAM scheme and a Frequency Shift Keying (FSK) scheme. The FQAM scheme enjoys the advantage of QAM in terms of high spectral efficiency and the advantage of FSK in terms of giving non-Gaussian characteristic to the interference signal.
In the wireless communication system, if an interferer cell uses the FQAM scheme, the statistical characteristic of the interference signal shows non-Gaussian characteristic. Accordingly, in order to accomplish the performance expected with the FQAM scheme, it is necessary to transmit data in the modulation scheme negotiated among the neighboring base stations.
Meanwhile, the FQAM scheme has a characteristic in which power per tone is irregular. The powers for the individual tones constituting a symbol are concentrated on one tone. As a result, only one tone (active tone) boosted in power as much as the number of the tones constituting one symbol is transmitted but the rest tones carry nothing. Although, if a pilot signal of a neighbor cell exists in one of the rest tones carrying nothing, the data transmitted in FQAM scheme in the cell in which the receiver is located does not contaminate the pilot signal of the neighbor cell; if the pilot signal of the neighbor cell hits the tone carrying data (active tone), this may cause significant contamination to the pilot signal of the neighbor cell.